1. Field of the Invention
The present invention relates in general to an apparatus and method for checking a link validity in a computer system, and more particularly to an apparatus and method for checking a link validity in a computer network, wherein, for the linking and referencing from one multimedia document to a different multimedia document in the computer network, desired information of the different multimedia document, such as last modified timestamp information indicative of a last modification time of the different multimedia document and latest version information of the different multimedia document, are stored in a validity check field, thereby assuring a link consistency.
2. Description of the Prior Art
At the present, a large amount of information is exchanged over a computer network such as the Internet in such a manner that computers connected to the computer network exchange information with other computers connected thereto. A technique for linking separated associated information together is generally used for effective utilization of multimedia documents in the computer network. It can be seen that links or hyperlinks currently used in computer networks have only information related to addresses of referenced multimedia documents. In this technique, a link is created whereupon an address thereof is used to search for a referenced multimedia document. As a result, the system first searches for a multimedia document via an associated link and then references its contents.
Referring to FIG. 1, there is shown an example of an Internet document (hypertext markup language (HTML) document) explaining the current economic situation of Korea. In this drawing, a link is used to specify a part describing the Korean economic growth rate by year during the 1990's with the aid of a bar graph for the better understanding of users reading the document. This link is indicated at the middle portion of FIG. 1 by “<imgsrc=“http://business.korea.ac.kr/image/TRgdpgrlv-95. gif”>”, wherein “TRgdpgrlv-95.gif” is a name of a referenced bar graph of FIG. 2 and “http://business.korea.ac.kr/image/TRgdpgrlv-95.gif” is an Internet address of the referenced bar graph.
Due to the development of computer systems and the Internet, a multimedia document editor and creation tools are universally used now, resulting in multimedia documents being frequently created, modified and deleted. For this reason, it is increasingly necessary to use a linked multimedia document after judging whether it is the very same one when an associated link was created.
Looking at the above example, a picture file indicated by “TRgdpgrlv-95.gif” exists, but its contents may be altered, an example of which is shown in FIG. 3. This example indicates the comparison between dollar and won expressions of Korean nominal GDP per head (95 series) in the 1990's. Hence, there is no further validity in the link “http://business.korea.ac.kr/image/TRgdpgrlv-95.gif” used in the Internet document of FIG. 1 to indicate the Korean GDP and economic growth rate by year (95 series) in the 1990's. In this case, if the link is used as it is, the document of FIG. 1 shows a picture file mismatched with the original contents.
The above-stated examples straightforwardly point out that there is a need for a procedure for checking the validity of a link before using the link. In particular, with the rapid development of an Internet network, the use of a method for linking multimedia documents to one another when they are created is on a rapidly increasing trend. In this regard, a conventional linking method for storing only addresses may erroneously transfer the contents of multimedia documents. The conventional linking method may further degrade the system performance and cause unexpected errors.
In the current computer system, a variety of information are together stored as metadata as a basic information unit. For example, information such as a date of creation, a date of modification and properties indicative of read only, hide, write and compress are together stored in each file.
However, in the computer network, each object, which is a fundamental unit for information processing, may be smaller in size than each file, and several individual objects may be present in each file. As a result, for metadata stored on a file basis, metadata regarding respective objects may not be actually stored and information regarding respective objects may not be applied in using the objects. As another example, metadata about objects must exist for object creation and modification in a distributed database.